Mild antimicrobial liquid cleansing formulations comprising hydroxy acid buffering compound or compounds as potentiator of antimicrobial effectiveness

ABSTRACT

Liquid skin cleansing compositions comprising (1) mild surfactant systems; (2) 0.5% to 9% by wt. of a hydroxy carboxylic compound or compounds which buffer the pH of the composition; (3) an antibacterial agent and (4) 1% to 99% water to potentiate the bactericidal activity are provided.

RELATED APPLICATIONS

This is a Continuation-in-Part of Ser. No. 08/810,114 filed Feb. 25,1997, now U.S. Pat. No. 5,914,300 which in turn is aContinuation-in-Part of 08/252,298, filed Jun. 1, 1994 now U.S. Pat. No.5,681,802.

BACKGROUND OF THE INVENTION

The present invention relates to one-phase liquid cleansing compositionshaving enhanced antimicrobial effectiveness. More specifically, theinvention relates to a hydroxy acid compound or compounds, moreparticularly lactic acid which potentiate the antibacterial activity ofliquid cleaning formulations by buffering the pH of the formulation suchthat the pH will rise no higher than 5.0, preferably between 2.5 to 5.0under in use conditions (as opposed to initial pH).

There is a large demand in the market for mild liquid cleansingformulations which additionally have an antibacterial effect.Antibacterial cleansers are preferred because they kill germs and mildpersonal cleansers are preferred to minimize skin irritation, dryness,etc. However, the combination of mild cleansing formulations and strongantibacterial effect is difficult to achieve. Thus, for example, whilesoaps provide antibacterial effects, they are not mild to the skin. Whenvery mild non-soap surfactants are used, antibacterial effect is greatlycompromised.

The balancing act between providing mildness and effective antibacterialeffectiveness is recognized for example in International Publication WO92/18100. In this publication, improved clinical mildness is said to beprovided through the use of a water soluble cationic polymer (see page10, lines 24-29). Cationic polymer is apparently used instead ofadditional ethoxylated surfactant because the percent of ethoxylatedmildness surfactant must be minimized in order not to affectantibacterial effectiveness (page 7, lines 4-6).

Another approach to providing mildness effect without affectingantibacterial properties is that which appears to be used by Dial in,for example, Liquid Dial Plus with Moisturizers Antibacterial Soap®.Here, mildness benefits are apparently provided by the use ofmoisturizing compounds rather than by the use of very mild surfactantsalone (which, as indicated above, compromises antibacterialeffectiveness).

In both cases, it can be readily seen that it is extremely difficult toprovide effective antibacterial action in the presence of very mildsurfactants, to use larger amounts of harsher surfactants or soaps andto mask the effects of the harshness by providing cationic mildnessconditioning agents (WO 92/18100) or moisturizers (as in the Dialproduct).

It would be greatly beneficial if antibacterial effectiveness could beprovided either by providing a compound or compounds which alone ortogether buffer pH of a liquid composition at a pH low enough to provideantibacterial effectiveness for that composition formulation (whilemaintaining stability of composition); or by providing a compound orcompounds which alone or together buffer pH of a liquid compositioncontaining anti-bacterial agent thereby enhancing (i.e., potentiating)the effect of the antibacterial agent even in compositions with verymild surfactant systems.

Fatty acids and their ester derivatives have been used to provideantimicrobial effectiveness in foods, pharmaceuticals and cosmetics(see, for example EP 0,244,144; U.S. Pat. No. 4,002,775; U.S. Pat. No.4,406,884; U.S. Pat. No. 4,997,851 and Kabara in JAOCS, vol. 61, No. 2,(February, 1984)).

The use of short chain fatty acids generally as potentiators ofgermicides is also known. These fatty acids, for example, have been usedas potentiators with halogenated germicides at high pH and withisethiazolones (see FR 2,223,049 and EP 488,606).

U.S. Pat. No. 3,218,260 to Lewandowski discloses cleaner compositionscontaining various organic or inorganic acids. The pH of thesecompositions (less than 2) is well below the pH of the skin cleansingcompositions of the present invention.

In none of these references is it taught or suggested that one or morecompounds be used either to enhance antibacterial effect in liquid skincleansing compositions or to potentiate antibacterial compounds whichmay already be present in liquid skin cleansing compositions at the pHspecified by the claims of the subject invention.

Further, none of these references relate to use of hydroxy carboxylicacid (e.g., lactic acid).

U.S. Pat. No. 5,132,037 to Greene et al. teaches aqueous compositions inwhich C₈ -C₂₂ free fatty acids may be used. All examples (palmitic,stearic) are clearly directed to longer chain fatty acids and there isabsolutely no recognition of the antibacterial or potentiating effect oflower chain fatty acids. Also, there is no teaching or suggestion ofhydroxy carboxylic acids.

U.S. Pat. No. 5,137,715 to Hoshowski et al. teaches shampoo conditionercompositions wherein the pH of the composition can be in the range of2.5 to 7.0. The invention requires a polymeric amidoamine compound(substantive compound which imparts conditioning and does not adverselyaffect foam of anionic; see column 11, line 63 to column 12, line 36).It is further taught that an acid is required to neutralize theamidoamine and one acid which is said to be used for this purpose iscitric acid (see column 13, lines 49-65).

The compositions of Hoshowski, while stable, were only stable when usingthe specific amidoamine of formula I (Example 13 of the patent notesthat an extremely similar amidoamine, represented by Formula V, causedinstability at pH below 6.0) and, according to examples, 2% citric acidwas used.

In general Hoshowski et al. makes clear that most amidoamines wouldcause instability. More specifically, applicants tried the amidoamine ofFormula I in compositions of the subject invention and also foundinstability. Applicants are not certain whether this instability was dueto large amounts of hydroxy acid (applicants use minimum 0.5% lacticacid versus 0.2% citric acid exemplified); whether it was due to thespecific hydroxy acid used; or whether it was due to the specificsurfactant system. What is clear, however, is that there is no suchinstability in the system of the invention without the amidoamine ofFormula I while there is such instability using the amidoamine in thesame system.

U.S. Pat. No. 5,002,680 to Schmidt et al. teach skin cleansing aerosolmousse emulsions comprising:

(A) 88% to 97% of a concentrate comprising:

(1) 3%-20% anionic or amphoteric;

(2) 0.05 to 5% polymeric skin feel aid;

(3) 10% to 60% moisturizers (which can be lactic acid); and

(4) water; and

(B) 3% to 12% propellant.

This reference differs from the subject compositions in a number ofways. First the lactic acid, if used, is used as moisturizing componentand must comprise 10% or greater of composition whereas upper level ofthe hydroxy carboxylic acid of invention (to provide bactericidaleffect) is about 9%. Further, the reference is not a single phasecomposition but comprises propellant (to form mousse). While not wishingto be bound by theory, bactericidal effect of hydroxy acid of inventionare believed to be due largely to single phase systems of invention. Ina multiphase, it is believed surfactant would not have time tosolubilize and enter liquid phase and therefore could not deliverantibacterial activity.

In short, applicants have now found that one or more hydroxy compoundsmay be used to buffer low pH within a defined low pH range and totherefore:

(1) enhance the antibacterial effect of liquid skin cleansingcompositions; and/or

(2) potentiate antimicrobial effect of liquid skin cleansingcompositions which already contain an antimicrobial agent.

The single phase compositions of the invention are free of amidoaminesgenerally and more specifically, of the amidoamines described in U.S.Pat. No. 5,137,715 to Hoshowski.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to liquid skin cleansing compositionscomprising:

(1) any mild surfactant system (i.e., any one or more surfactants whichalone or together are demonstrated by clinical tests to be milder thansoap itself) in an amount of from about 1-99% by wt., preferably 2-85%by wt., more preferably 3-40% by wt. surfactant system;

(2) 0.5 to about 9%, preferably 0.5 to 5% by weight of a hydroxycarboxylic compound or compounds (e.g., lactic acid) which alone ortogether buffer the pH of the liquid skin cleanser composition such thatthe pH is no higher than 5.5 under in-use conditions (i.e., 1:0.5 to1:100 dilution, preferably 1:1 to 1:25 dilution of product in H₂ O); and

(3) 1% to 99% by wt., preferably 15 to 97%, most preferably 60 to 97% bywt. water.

More specifically, the composition may comprise:

(1) 1% to 99% by wt. of surfactant system comprising:

(a) 1 to 30% by wt. of at least one anionic surfactant;

(b) 0.5% to 15% amphoteric surfactant;

(2) 0.5 to 9% hydroxy acid; and

(3) 1% to 99% water.

In a second embodiment of the invention, the liquid skin cleansingcomposition comprises 0.0001% to 5% by weight of an antibacterial agentand the buffering compound or compounds act to potentiate theantimicrobial effect of the composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the effect of lactic acid concentration on the bactericidalactivity of liquid skin cleansing formulation of the invention whichcontains an antibacterial agent (e.g., Triclosan or DP300®). As seen,bactericidal activity of the formulation increases with lactic acidcontent up to about 9%. At 10% and above, bactericidal activity does notincrease with increasing lactic acid content.

As shown by Example 3, the particular antibacterial agent selectedshould have no bearing on the lactic acid effect (i.e., low pH inducedby lactic acid is what is causing effect although it should be notedthat effect of Triclocarban was superior even to effect of pH alone).

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to liquid skin cleansing compositionscomprising 1 to 99% by weight, preferably 2 to 85%, more preferably 3 to40% of a mild surfactant system comprising one or more surfactants whichalone or together have been clinically tested to be milder than soapitself as measured by zein solubilization test (soap yields 80% zeinsolubilized). Preferably, the mildness is such that zein solubilizationis in the range 10-60% solubilization.

A number of anionic, nonionic, cationic and amphoteric surfactants maybe employed in the surfactant system of the invention provided of coursethat the surfactant, if used alone, or surfactant mixture is milder thanwould be soap itself as measured by the zein solubilization test.

Among suitable anionic co-actives are the alkyl ether sulfates, acylisethionates, alkyl ether sulfonates, sarcosinates, sulfosuccinates,taurates and combinations thereof. Among suitable amphoteric co-activesmay be included alkylbetaines, amidopropyl betaines, amidopropylsultaines and combinations thereof.

Alkyl ether sulfates of the present invention will be of the generalformula R--(OCH₂ CH₂)_(n) OSO₃ --M⁺ wherein R ranges from C₈ -C₂₀ alkyl,preferably C₁₂ -C₁₅ alkyl, n is an integer from 1 to 40, preferably from2 to 9, optimally about 3, and M⁺ is a sodium, potassium, ammonium ortriethanolammonium cation.

Typical commercial co-actives of this variety are listed in the Tablebelow:

    ______________________________________                                                                   Physical Manufac-                                  Trademark  Chemical Name   Form     turer                                     ______________________________________                                        Steol CS 330                                                                             Sodium Laureth Sulfate                                                                        Liquid   Stepan                                    Standopol ES-3                                                                           Sodium Laureth Sulfate                                                                        Liquid   Henkel                                    Alkasurf ES-60                                                                           Sodium Laureth Sulfate                                                                        Paste    Alkaril                                   Cycloryl TD                                                                              TEA Laureth Sulfate                                                                           Paste    Cyclo                                     Standapol 125-E                                                                          Sodium Laureth-12 Sulfate                                                                     Liquid   Henkel                                    Cedepal TD407MF                                                                          Sodium Trideceth Sulfate                                                                      Paste    Miranol                                   Standopol EA-2                                                                           Ammonium Laureth Sulfate                                                                      Liquid   Henkel                                    ______________________________________                                    

Alkyl ether sulfonates may also be employed for the present invention.Illustrative of this category is a commercial product known as AvenelS-150 commonly known as a sodium C₁₂ -C₁₅ Pareth-15 sulfonate.

Another co-active type suitable for use in the present invention is thatof the sulfosuccinates. This category is best represented by themonoalkyl sulfosuccinates having the formula RO₂ CCH₂ CH(SO₃--Na⁺)COO--M⁺ ; and amido-MEA sulfosuccinates of the formula RCONHCH₂CH₂ O₂ CCH₂ CH (SO₃ M⁺)COO--M⁺ ; wherein R ranges from C₈ -C₂₀ alkyl,preferably C₁₂ -C₁₅ alkyl and M⁺ is a sodium, potassium, ammonium ortriethanolammonium cation. Typical commercial products representative ofthese co-actives are those listed in the Table below:

    ______________________________________                                                                    Physical                                                                              Manufac-                                  Trademark  Chemical Name    Form    turer                                     ______________________________________                                        Emcol 4400-1                                                                             Disodium lauryl  Solid   Witco                                                Sulfosuccinate                                                     Witco C5690                                                                              Disodium Cocoamido MEA                                                                         Liquid  Witco                                                Sulfosuccinate                                                     McIntyre Mackanate                                                                       Disodium Cocoamido MEA                                                                         Liquid  McIntyre                                  CM40F      Sulfosuccinate                                                     Schercopol CMSNa                                                                         Disodium Cocoamido MEA                                                                         Liquid  Scher                                                Sulfosuccinate                                                     Emcol 4100M                                                                              Disodium Myristamido MEA                                                                       Paste   Witco                                                Sulfosuccinate                                                     Schercopol Disodium Oleamido MEA                                                                          Liquid  Scher                                     Varsulf S13333                                                                           Disodium Ricionoleamido                                                                        Solid   Scherex                                              MEA Sulfosuccinate                                                 ______________________________________                                    

Sarcosinates may also be useful in the present invention as a co-active.This category is indicated by the general formula RCON(CH₃)CH₂ CO₂ --M⁺,wherein R ranges from C₈ -C₂₀ alkyl, preferably C₁₂ -C₁₅ alkyl and M⁺ isa sodium, potassium ammonium or triethanolammonium cation. Typicalcommercial products representative of these co-actives are those listedin the Table below:

    ______________________________________                                                                  Physical                                            Trademark  Chemical Name  Form    Manufacturer                                ______________________________________                                        Hamposyl L-95                                                                            Sodium Lauroyl Solid   W. R. Grace                                            Sarcosinate                                                        Hamposyl TOC-30                                                                          TEA Cocoyl/Sarcosinate                                                                       Liquid  W. R. Grace                                 ______________________________________                                    

Taurates may also be employed in the present invention as co-actives.These materials are generally identified by the formula RN⁺ (CH₃)₂ CH₂CO₂ M⁺, wherein R ranges from C₈ -C₂₀ alkyl, preferably C₁₂ -C₁₅ alkyl,R¹ ranges from C_(1-C) ₄ alkyl, and M⁺ is a sodium, potassium, ammoniumor triethanolammonium cation. Typical commercial products representativeof these co-actives are those listed in the Table below:

    ______________________________________                                                                   Physical Manufac-                                  Trademark                                                                              Chemical Name     Form     turer                                     ______________________________________                                        Igepon TC 42                                                                           Sodium Methyl Cocoyl Taurates                                                                   Paste    GAF                                       Igepon T-77                                                                            Sodium Methyl Oleoyl Taurate                                                                    Paste    GAF                                       ______________________________________                                    

Within the category of amphoterics there are three general categoriessuitable for the present invention. These include alkylbetaines of theformula RN⁺ (CH₃)₂ CO₂ -M⁺, amidopropyl betaines of the formula RCONHCH₂CH₂ CH₂ N⁺ (CH₂)₂ CH₂ CO2--M⁺, and amidopropyl sultaines of the formulaRCONHCH₂ CH₂ N⁺ (CH₃)₂ CH₂ SO₃ --M⁺ wherein R ranges from C₈ -C₂₀ alkyl,preferably C₁₂ -C₁₅ alkyl, and M⁺ is a sodium potassium, ammonium ortriethanolammonium cation. Typical commercial products representative ofthese co-actives are found in the Table below:

    ______________________________________                                                                   Physical Manufac-                                  Trademark  Chemical Name   Form     turer                                     ______________________________________                                        Tegobetaine F                                                                            Cocamidopropyl Betaine                                                                        Liquid   Gold-                                                                         schmidt                                   Lonzaine C Cocamidopropyl Betaine                                                                        Liquid   Lonza                                     Lonzaine CS                                                                              Cocamidopropyl  Liquid   Lonza                                                Hydroxysultaine                                                    Lonzaine 12C                                                                             Coco-Betaine    Liquid   Lonza                                     Schercotaine MAB                                                                         Myristamidopropyl Betaine                                                                     Liquid   Lonza                                     Velvetex OLB-50                                                                          Oleyl Betaine   Paste    Henkel                                    ______________________________________                                    

Within the broad category of liquid actives, the most effective are thealkyl sulfates, alkyl ether sulfates, alkyl ether sulfonates,sulfosuccinates, and amidopropyl betaines.

Another preferred surfactant is an acyl isethionate having the formula:##STR1## in which R denotes a linear or branched alkyl group and Mdenotes an alkali metal or alkaline earth metal or an amine.

Another surfactant which may be used are the monoalkyl ordialkylphosphate surfactants.

Another mild surfactant which may be used, preferably used as primarysurfactant in combination with other surfactants noted above, is sodiumcoco glyceryl ether sulfonate. While desirable to use because of itsmildness properties, this coco AGS alone does not provide optimum lathercreaminess. A sodium 90/10 coconut/tallow alkyl AGS distribution ispreferred for creaminess. Salts other than the sodium salt such as TEA-,ammonium, and K-AGS and chain length distributions other than 90/10coconut/tallow are usable at moderate levels. Also, some soap may beadded to improve lather volume and speed of lathering. Certain secondaryco-surfactants used in combination with AGS can also provide a creamierand more stable lather. These secondary surfactants should also beintrinsically mild. One secondary surfactant that has been found to beespecially desirable is sodium lauroyl sarcosinate (trade name HamposylL, made by Hampshire Chemical).

The amphoteric betaines and sultaines noted above can be used as thesole surfactant, but are more preferred as a co-surfactant. Nonionicsgenerally should not be used as the sole surfactant in this product ifhigh foaming is desirable; however, they can be incorporated as aco-surfactant.

Nonionic and cationic surfactants which may be used include any one ofthose described in U.S. Pat. No. 3,761,418 to Parran, Jr., herebyincorporated by reference into the subject application.

Soaps can be used at levels of about 1-10%. Soaps can be used at higherlevel provided that the surfactant mixture is milder than soap. Thesoaps may be added neat or made in situ via adding a base, e.g., NaOH;to convert free fatty acids.

Of course, as noted above, soaps should only be used as cosurfactants tothe extent that the surfactant system is milder than soap alone.

Surfactant may comprise 1% to 30% by wt. of at least one anionic and0.5% to 15% amphoteric.

A preferred surfactant active system is one such that acyl isethionatecomprises 1 to 15% by weight of the total composition, an anionic otherthan acyl isethionate (e.g., ammonium lauryl ether sulfate) comprises 1to 15% by weight of the total composition and amphoteric comprises 0.5to 15% by weight of the total composition.

BUFFERING COMPONENT

The second critical component of the liquid compositions of theinvention is the compound or compounds which alone or together bufferthe pH of the formulation under in-use condition such that the pH isfrom about 2.5 to 5.5, preferably 3.0 to 5.0, more preferably 3.5 to5.0.

By in-use is meant dilution of 1:0.5 to 1:100, preferably 1:1 to 1:25 ofthe product in water during use.

This compound or compounds is a hydroxy carboxylic acid which lowers pHof the compositions in use to 2.5 to 5.5 and buffers at this pH.

The hydroxy carboxylic acids include any organic compound having atleast one carboxylic acid group and at least one hydroxyl group.Preferably, the chain length of the acid should be C₂ to C₁₈, morepreferably C₂ to C₁₂. Among the many acids which may be used includecitric acid, lactic acid, glycolic acid, α-hydroxy C₈ acid, α-hydroxyC₁₆ acid, acylated citric acid and β-hydroxybutyric acid. A preferredacid is lactic acid.

In a second embodiment of the invention, the liquid skin cleansingcompositions of the subject invention must contain an antibacterialagent. In this embodiment of the invention, the buffering component orcompounds described above not only may provide antibacterial effect onits own, but also enhances (potentiates) the antibacterial effectivenessof the antibacterial agent.

The antibacterial agent can be present at a level of from about 0.001%to about 5%, typically from about 0.01% to about 2%, and preferably fromabout 0.01% to about 1.5% by weight of the composition. The level isselected to provide the desired level of antibacterial activity and canbe modified as desired. The preferred antibacterial agent is2-hydroxy-4,2',4'-trichlorodiphenylether (DP300). Other antibacterialagents are set out below. Many antibacterial agents, known to thoseskilled in the art and disclosed in e.g., U.S. Pat. Nos. 3,835,057 and4,714,563, both incorporated hereinbefore by reference, may be used.

Antimicrobials

Suitable antibacterial agents which may be used in the subject invention(i.e., in one embodiment of the invention) include:

2-hydroxy-4,2',4'-trichlorodiphenylether (DP300);

2,6-dimethyl-4-hydroxychlorobenzene (PCMX);

3,4,4'-trichlorocarbanilide (TCC);

3-trifluoromethyl-4,4'-dichlorocarbanilide (TFC);

2,2'-dihydroxy-3,3',5,5',6,6'-hexachlorodiphenylmethane;

2,2'-dihydroxy-3,3',5,5'-tetrachlorodiphenylmethane;

2,2'-dihydroxy-3,3',dibromo-5,5'-dichlorodiphenylmethane;

2-hydroxy-4,4'-dichlorodiphenylether;

2-hydroxy-3,5',4-tribromodiphenylether; and

1-hydroxyl-4-methyl-6-(2,4,4-trimethylpentyl)-2(1H)-pyridinone(Octopirox).

Other suitable antimicrobials include:

Benzalkonium chloride;

Benzethonium chloride;

Carbolic acid;

Cloflucarbon (Irgasan CF3;4,4'-dichloro-3-(trifluoromethyl)carbanilide);

Chlorhexidine (CHX; 1,6-di(4'-chlorophenyl-diguanido) hexane);

Cresylic acid;

Hexetidine (5-amino-1,3-bid(2-ethylhexyl)-5-methylhexahydropyrimidine);

lodophors;

Methylbenzethonium chloride;

Poly(hexamethylene biguanide) hydrochloride (Cosmocil CQ)

Povidone-iodine;

Tetramethylthiuram disulfide (TMTD; Thiram);

Tribrominated salicylanilide.

In addition to a mild surfactant compound or compounds, the pH bufferingcompound or compounds, water and optionally (or as required in oneembodiment), antimicrobial agent, the liquid skin cleansing compositionsmay contain optionals as described below.

Each of the above components can be incorporated in an aqueous vehiclewhich may, in addition, include such materials as organic solvents, suchas ethanol, thickeners, such as carboxymethylcellulose, magnesiumaluminum silicate, hydroxyethylcellulose, methylcellulose or carbopols;perfumes; sequestering agents, such as tetrasodiumethylenediaminetetraacetate (EDTA), EHDP or mixtures in an amount of0.01 to 1%, preferably 0.01 to 0.05%; and coloring agents, opacifiersand perlizers such as zinc stearate, magnesium stearate, TiO₂, EGMS(ethylene glycol monostearate) or Lytron 621 (Styrene/Acrylatecopolymer); all of which are useful in enhancing the appearance orcosmetic properties of the product.

The following preservatives may also be used in the liquid skincleansers of the invention:

    ______________________________________                                        LIQUID SKIN CLEANSER PRESERVATIVES                                            PRESERVATIVE                                                                            CHEMICAL NAME                                                       ______________________________________                                        Bronopol  2-Bromo-2-nitropropane-1,3,diol                                     Dowicil 200                                                                             cis Isomer of 1-(3-chloroallyl)-3,5,5-triaza-1-                               azoniadamantane-chloride OR Quaternium 15                           Glycacil  3-Iodo-2-propynyl butyl carbamate                                   Glydant XL 1000                                                                         DMDM Hydantoin OR dimethyloldimethylhydantoin                       Glydant Plus                                                                            DMDM Hydantoin and 3-iodo-2-propynyl butyl                                    carbamate                                                           Formaldehyde                                                                            Formaldehyde                                                        Germall 11                                                                              N-(Hydroxymethyl)-N-(1,3-dihydroxymethyl-2,5-                                 dioxo-4-imidazolidinyl)-N'-(hydroxymethyl) urea OR                            Diazolidinyl urea                                                   Germall 115                                                                             N,N'-methylene-bis-[N'-1-(hydroxymethyl)-2,,5-dioxo-                          4-imidazolidinyl]urea OR imidazolidinyl urea                        Glutaraldehyde                                                                          Glutaraldehyde                                                      Kathano CG                                                                              Mixture of 5-chloro-2-methyl-4-isothiazoline-3-one-                           and 2-methyl-4-isothiazoline-3-one OR Mixture of                              methyl, chloromethyl isothiazolinone, and methyl                              isothiazolinone                                                     Parabens  Methyl Paraben, and Ethyl Paraben, and Propyl                                 Paraben and Buryl Paraben OR those esters of                                  p-hydroxybenzoic acid                                               Phenoxyethanol                                                                          2-Phenoxyethanol                                                    Salicylic Acid                                                                          Salicylic Acid QR o-Hydroxybenzoic acid                             Sorbic Acid                                                                             Sorbic Acid, Potassium Sorbate                                      ______________________________________                                    

Coconut acyl mono- or diethanol amides as suds boosters, and stronglyionizing salts such as sodium chloride and sodium sulfate may be used toadvantage.

Antioxidants such as, for example butylated hydroxytoluene (BHT) may beused advantageously in amounts of about 0.01% or higher if appropriate.

Cationic conditioners which may be used include Quatrisoft LM-200(Polyquaternium-24); polyethylene glycols such as

    ______________________________________                                        Polyox       WSR-205       PEG 14M,                                                        WSR-N-60K     PEG 45M, or                                                     WSR-N-750     PEG 7M; and                                        Merquat Plus 3330 - Polyquaternium 39.                                        ______________________________________                                    

Thickeners which may be used include Americoll Polymer HM 1500(Nonoxynyl Hydroethyl Cellulose); Glucan DOE 120 (PEG 120 Methyl GlucoseDioleate).

Unless stated otherwise, the percentages in the specification, examplesand claims are percentages by weight.

Except in the operating and comparative examples, or where otherwiseexplicitly indicated, all numbers in this description indicating amountsof material (or conditions of reaction and/or use) are to be understoodas modified by the word "about".

The following examples are intended for illustrative purposes only andshould not be construed to limit the invention in any way.

EXAMPLES

An In vitro Bactericidal Kill Test is used to measure antimicrobialactivity in the examples which follow. Methodology for the test is setforth below:

IN VITRO BACTERICIDAL KILL TEST

An in vitro bactericidal test was used to determine the antibacterialeffect of products on Staphylococcus aureus ATCC #6538 during a shortcontact time. One milliliter (about 10⁸ cells) of bacteria was exposedfor one minute to a one-percent solution of liquid skin cleansingcomposition. The sample was added to additional water, mixed, andfurther diluted in 0.1% peptone. Duplicate samples of appropriatedilutions were plated on neutralizing media. In addition, the bacterialculture was plated to determine the actual number of organismsinoculated. the plates were incubated at 34° C. for 48 hours andenumerated. The CFU/ml (colony forming units per milliliter) fromdilutions with plate counts in the range of 30-300 were averagedtogether to produce the final CFU/ml.

The results may be expressed as the log of the CFU/ml. The culturecontrol indicates the actual number of bacteria inoculated while thewater control reflects the number of organisms recovered in the absenceof product. The lower the number, the more effective the solution was inkilling the bacteria.

In this assay, a sampling error of approximately 0.5 log is likely,therefore differences of 0.5 log between products may not besignificant. As a result, the data should be viewed in terms of trendsrather than as absolute numbers.

Example 1

Applicants carried out an experiment showing that lactic acidconcentration on the bacteriocidal activity of liquid skin cleansingformulation. As seen in FIG. 1, the bacteriocidal activity of theformulation increases with lactic acid content up to about 9%. At 10%and above, bactericidal activity does not increase with increasinglactic acid content.

    ______________________________________                                        INGREDIENT              % BY WEIGHT                                           ______________________________________                                        Anionic (Acyl Isethionate)                                                                            1 to 15%                                              Anionic Other than Acyl Isethionate (e.g., SLES)*                                                     1 to 15%                                              Amphoteric Surfactant** 5 to 15%                                              pH Buffering (Lactic Acid)                                                                            1 to 5%                                               Sequestrant (EDTA or EHDP)                                                                            0.01 to 0.1%                                          Moisturizer (e.g., Cationic Polymer)                                                                  0.05 to 3.0%                                          Additives (e.g., Dyes, Perfumes)                                                                      0 to 10%                                              Water                   Balance                                               ______________________________________                                         *SLES  sodium lauryl ether sulfate                                            **Cocoamidopropyl betaine                                                

Example 2

The compound or compounds of the invention may also be used in thefollowing formulations.

    ______________________________________                                        COMPONENT           % BY WEIGHT                                               ______________________________________                                        FORMULATION 1                                                                 Sodium Isethionate  3-5%                                                      Sodium Alkene Benzene Sulfonate                                                                   1-3%                                                      Sodium Laureth Sulfate                                                                            3-5%                                                      Sodium Cocoyl Isethionate                                                                          8-12%                                                    Sodium Tallow/Coconut Soap                                                                        1-3%                                                      Preservative (e.g., Methylparaben)                                                                .1-.5%                                                    Sequestrants        .01-.05%                                                  Fatty Acid (e.g., Stearic Acid)                                                                    7-10%                                                    Sulfosuccinate      3-5%                                                      Water plus minors   to balance                                                FORMULATION 2                                                                 Sodium Cocoyl Isethionate                                                                         5-8%                                                      Cocamidopropyl Betaine                                                                            5-8%                                                      Sulfosuccinate      2-5%                                                      Fatty Acid          6-9%                                                      Sodium Isethionate  1-3%                                                      Silicone Emulsion   3-7%                                                      Sequestrant         .01-.05%                                                  Water plus minors   to balance                                                ______________________________________                                    

Example 3

Applicants sought to show that the antibacterial effect provided by lowpH compositions comprising lactic acid is not dependent on the specificantibacterial compound selected. In this regard, applicants preparedcompositions as noted below:

    ______________________________________                                        CONTROL                                                                       COMPONENT         % BY WEIGHT                                                 ______________________________________                                        Sodium Cocoyl Isethionate                                                                          6-8%                                                     Sodium Laureth Sulfate                                                                             5-7%                                                     Cocamidopropyl Betaine                                                                             1-3%                                                     Cationic Polymer  0.1%                                                        EDTA                 0.01-0.03%                                               Antibacterial     0.25%                                                       Lactic Acid          .sup. 0.1-5.0%*                                          Water             To balance                                                  ______________________________________                                         *Range varied according to pH. Approximately 0.1% was actually used in th     experiments conducted.                                                   

Using the bacteriocidal kill test described above, various antibacterialcompounds were used and results set forth below:

    ______________________________________                                                              pH               Log.sub.10                             Organism                                                                             Sample         (Undiluted)                                                                             CFU/ml CFU/ml                                 ______________________________________                                        S. aureus                                                                            S. aureus Control Count                                                                      --        3.80 × 10.sup.8                                                                8.58                                   ATC 6538                                                                             Water          --        2.62 × 10.sup.8                                                                8.42                                          Control (Composition                                                                         4.00      6.20 × 10.sup.7                                                                7.79                                          alone)         4.54      1.47 × 10.sup.8                                                                8.17                                                         4.88      1.59 × 10.sup.8                                                                8.20                                          Control + 0.25%                                                                              4.00      5.70 × 10.sup.7                                                                7.76                                          Cosmocil CQ.sup.1/                                                                           4.50      1.54 × 10.sup.8                                                                8.19                                                         4.96      1.65 × 10.sup.8                                                                8.22                                          Control + 0.25%                                                                              4.02      3.50 × 10.sup.7                                                                7.54                                          PCMX.sup.2/    4.50      1.48 × 10.sup.8                                                                8.17                                                         4.97      1.47 × 10.sup.8                                                                8.17                                          Control + 0.25%                                                                              4.01      4.60 × 10.sup.7                                                                7.66                                          Triclosan (DP300).sup.3/                                                                     4.48      1.05 × 10.sup.8                                                                8.02                                                         5.01      1.46 × 10.sup.8                                                                8.16                                          Control + 0.25%                                                                              3.97      7.00 × 10.sup.6                                                                6.85                                          Triclocarban (TCC).sup.4/                                                                    4.54      3.90 × 10.sup.7                                                                7.59                                                         4.97      4.60 × 10.sup.7                                                                7.66                                          Control + 0.25%                                                                              3.88      8.50 × 10.sup.7                                                                7.93                                          Benzalkonium Chloride                                                                        4.56      1.82 × 10.sup.8                                                                8.26                                                         4.80      1.88 × 10.sup.8                                                                8.27                                          Control + 0.25%                                                                              4.04      8.60 × 10.sup.7                                                                7.93                                          Chlorhexidine  4.49      1.45 × 10.sup.8                                                                8.16                                                         4.97      2.02 × 10.sup.8                                                                8.31                                   ______________________________________                                         .sup.1/ Poly(hexamethylene biguanide)hydrochloride                            .sup.2/ 2,6dimethyl-4-hydrochlorobenzene                                      .sup.3/ 2hydroxy-4,2',4trichlorodiphenylether                                 .sup.4/ 3,4,4trichlorocarbanilide                                        

As can be seen from the results, it was low pH (i.e., using lactic acidbuffer) which provided enhanced antibacterial effect relative to waterregardless of which antibacterial agent was used (except in case ofTriclorcarban where antibacterial effect was superior even to pHeffect). This clearly shows that the enhanced bactericidal activity oflactic acid (as observed in FIG. 1) is independent of antibacterialagent chosen.

Example 4

In a separate experiment, applicants prepared the following formulationcontaining NaOH and slightly more lactic acid to both the compositions.

    ______________________________________                                        CONTROL                                                                       COMPONENT          % BY WEIGHT                                                ______________________________________                                        Sodium Laureth Sulfate                                                                           4-5%                                                       Sodium Olefin Sulfonate                                                                          2-3%                                                       Cocamidopropyl Betaine                                                                           2-4%                                                       Cationic Polymer     2%                                                       Ethylene Glycol Monostearate                                                                       1%                                                       NaOH               ˜40%                                                 Lactic Acid        ˜2%                                                  Perfume, Preservatives & Water                                                                   To Balance                                                 ______________________________________                                    

Again, using the bacteriocidal test described above, variousantibacterial compounds were used and results set forth below.

    ______________________________________                                        BASIN INOCULATION TEST (BIS 102798)                                                                                 Log.sub.10                              Organism                                                                              Sample      pH (Undiluted)                                                                           CFU/ml CFU/ml                                  ______________________________________                                        S. aureus                                                                             S. aureus   --         2.55 × 10.sup.8                                                                8.41                                    ATCC 6538                                                                             Control Count                                                                 Water       --         2.38 × 10.sup.6                                                                8.38                                            Control     4.0        1.21 × 10.sup.6                                                                6.08                                                        4:5        1.36 × 10.sup.6                                                                6.13                                                        5.5        1.20 × 10.sup.7                                                                7.08                                            Control +   4.0         6.5 × 10.sup.5                                                                5.81                                            0.25%       4.5        1.24 × 10.sup.6                                                                6.09                                            Cosmocil CQ 5.5        1.55 × 10.sup.7                                                                7.19                                            Control +   4.4        1.69 × 10.sup.5                                                                5.23                                            0.25% PCMX  4.5        1.04 × 10.sup.6                                                                6.02                                                        5.5        1.21 × 10.sup.7                                                                7.08                                            Control +   4.0        5.10 × 10.sup.5                                                                5.71                                            0.25%       4.5        1.75 × 10.sup.6                                                                6.24                                            Triclosan   5.5        1.15 × 10.sup.7                                                                7.06                                            Control +   4.0        7.10 × 10.sup.5                                                                5.85                                            0.25%       4.5        1.24 × 10.sup.6                                                                6.09                                            Triclocarban                                                                              5.5        1.96 × 10.sup.7                                                                7.29                                            Control + 0.25%                                                                           4.0        4.00 × 10.sup.5                                                                5.60                                            Benzalkonium                                                                              4.5        7.10 × 10.sup.5                                                                5.85                                            Chloride    5.5        1.10 × 10.sup.7                                                                7.04                                            Control +   4.0        6.50 × 10.sup.5                                                                5.81                                            0.25%       4.5        1.31 × 10.sup.6                                                                6.12                                            Chlorhexidine                                                                             5.5        4.90 × 10.sup.7                                                                7.69                                    Control was used as the base                                                  ______________________________________                                    

We claim:
 1. A skin cleansing composition comprising:(1) 1% to 15% byweight acyl isethionate; (2) 1% to 15% by weight of an an ionicsurfactant other than acyl isethionate; (3) 5% to 15% by weight of anamphoteric surfactant; (4) 0.5% to 9% by weight lactic acid; (5) 0.001%to 5% by weight of an antibacterial agent wherein said antibacterialagent is selected from the group consistingof:2,6-dimethyl-4-hydroxychlorobenzene; 3,4,4'-trichlorocarbanilide;Benzalkonium chloride; Chlorhexidine; Poly(hexamethylene biguanide)hydrochloride and mixtures thereof; and (6) balance water, wherein pH isfrom about 2.5 to less than 5.0.
 2. A composition according to claim 1,wherein pH is from about 3.0 to less than 5.0.